Interlay for plywood sheets used for doors, and the like



Jun 9, 1959 2,889,594'

ETSl USED FOR DooRs,- AND THE LIKE I F. FEL'IERBORN NTERLAY FOR eLYwoon SHE Filed March 15p 1955 United States iPatent nvTEnLAY Fon PLYwoon SHE-nrs Usnnrorr. nooRs, AND THE LIKE Fritz Feuerborn, Wiedenbruck, Westphalia, Germany Application March 15, 1955, Serial No. 494,481 In Germany October 1, 1948 Public Law 619, August 23, 1954 Patent expires October 1, 1968 3 Claims. (Cl. 20-91) The invention refers to an interlay for plywood sheets, used in the construction of doors and the like.

Hitherto, the interlays for plywood door sheets were made mostly of wood. In this connection the interlays, in order not to make the door too heavy Iand to save timber were made of longitudinally running strips of wood, between which at certain intervals, were laid small wooden blocks, so that corresponding cavities were formed, or lattice work structures were made with larger or smaller cavities. These interlays were then, in the usual form, covered with sheets of veneer or plywood. In order that the straight strips, running the full length do not crack under the pressure they must have a thickness of at least l5 mm.

These known interlays of plywood however, hrow great faults, namely insofar as the interlay strips must be spot glued round about their extremes. Such glued strips of plywood could then be drawn away from each other sideways so that also elliptically shaped cells would result. With interlays formed this way, when the necessary veneer or sheets are glued on to each side, hermetically sealed cavities are formed. By pressing on a hot press a considerable amount of steam is, however, developed which cannot escape and which collects in these cavities so that a steam pressure of several atmospheres is created, with the result that when the press is opened, the plates formed in this way spring apart. Such interlays can thus only be employed with use of cold or warm glues, which as a result of the long time required in the press makes rational working impossible, The preparation of such interlays also requires much working time.

According to the invention, an interlay for plywood slabs for doors and the like, comprising corrugated thin strips of plywood, or a similar permanent formation having -a stifening effect, which form a corresponding number of separately arranged single cavity cells loosely supporting each other at fixed intervals and with their extremes bedded in pairs, into recesses in the upper and lower cross bars of the frame of the door or the like, these cross bars having grooves for the escape of hot air vapour produced during the manufacture of the plywood slabs.

The invention will be described further by way of example with reference to the accompanying drawings in which:

Fig. l shows a partly sectioned front view of a door provided with an interlay;

Fig. 2 shows a plan view of such a door.

According to the invention an interlay )for plywood slab is to be built of a certain number of strips a, which are either of corrugated formation as shown in the drawing or of similar repetitive formation having a stiifening eiect.

Patented 2 The separate strips a lie rection beside each other with-the crests and loops of adjacent undulat'ed`st`rips projecting in opposite directions to each other whereby'separately arranged single cavity cells orf-elliptical, polygonal, square-orfotheralternate form are produced. It is a particular advantage of the invention that the various strips need not equal thevtotal length of the door, but may consist of several separate pieces which can then be laid correspondingly into each other (as shown in dotted section in Fig. 1). Thereby it is possible to utilize all Waste strips and shorter lengths which are obtained during the production of wood sheets. The upper and lower extremities al of each pair of strips t into recesses which for example are provided in the cross bars b of the frame surrounding the interlay. The interlays are covered on both back and front surfaces with sheets c, c1 of plywood, veneer or the like.

In order to enable the quantities of steam which are formed inside the interlay by the pressing on of the two plywood, veneer or cover sheets in the hot press, to escape, one or more grooves d are provided in the cross bars b. The corrugated strips standing on their edge have great resistance to cracking and can even for high power presses be laminated and veneered. Corrugated strips for instance formed into plywood 18/10 mm. thick may be pressed with an equally strong force as a strip interlay as already mentioned of l5 mm. thick wooden strip, without the corrugated strips cracking in the smallest degree. Although a saving of great quantities of wood results from the invention, rigidity is not prejudiced.

The strips should with yadvantage be made of plywood composed of mutually suitable types of wood, in which connection the use of the waste products in the aeroplane industry should have particular consideration.

Doors and the like produced according to the invention are not only exceedingly simple and cheaply manufactured, but in addition are yalso of the greatest possible durability.

It will, of course, be understood that various details of construction may be varied through a wide range without departing from the principles of this invention and it is, therefore, not the purpose to limit the patent granted hereon otherwise than necessitated by the scope of the appended claims.

I claim:

l. In a door construction o-f the type described the combination of a door frame, said door frame including cross bars at opposing end portions thereof, a pair of veneer sheet covering members secured to opposing sides of said door frame in spaced relationship to each other, a plurality of thin corrugated strips of plywood mounted in said door frame and interposed between the said sheet covering members in such a fashion that the corrugations thereof are arranged perpendicularly to the normal planar surfaces of the sheet covering members, at least one of the said strips comprising a plurality of individual lengths of plywood arranged so that the ends of adjacent individual lengths of plywood overlie one another and said strips also being arranged in side by side `and parallel relationship with parts of the surfaces of adjacent strips only loosely contacting each `other to form a plurality of substantially elliptical cells within the interior of the door and the ends of each of said strips being loosely mounted in said door frame cross bars, and said cross bars being further provided with recesses in open communication with the interior of the door and the atmosphere, said recesses serving as escape ports for venting hot air vapours to the atmosphere during the securing of June 9, 1.959;y

the sheet covering members to the said cross bars and v to the corrugated plywood strips.

2. In the combination as set forth in claim 1 wherein the crests and loops of adjacent corrugated strips project in opposite directions to each other.

3. The combination as set forth in claim 1 wherein the corrugations are arranged in a recurring pattern in each of said plywood strips. Y

References Cited in the ie of this patent UNITED STATES PATENTS 2,324,299 Neale July 13, 1943 FOREIGN PATENTS Great Britain Nov. 27, 1936 Australia Sept. 23, 1942 Great Britain Oct. 13, 1943 Great Britain Dec. 30, 1946 Sweden Aug. 31, 1948 Great Britain June 21, 1949 Germany July 5, 1951 France Mar. 5, 1952 France Apr. 1, 1953 

